Absorption refrigeration



Aug. 23, 1955 c. T. ASHBY ET AL 2,715,813

ABSORPTION REFRIGERATION I 1 Filed Dec. 28, 1951 Rs 6404 Z'As/wy (194925.; i Ma /P W (Ill United rates Patent @ffice 2,715,818 Patented Aug.23, 1955 ABSORPTION REFRIGERATION Carl T. Ashby and Charles A. Miller,Evansville, Ind.,

assignors to Servel, Inc., New York, N. Y., a corporation of DelawareApplication December 23, 1951, Serial No. 263,731

Claims. (Cl. 62-119.5)

Our invention relates to refrigerating systems of the absorption typewherein an inert gas is used to maintain an equal total pressurethroughout the system and more particularly to refrigerating systems ofthis type wherein a quantity of inert gas is held in reserve in anormally inactive part of the system under normal operating conditionswhich reserved gas is conveyed to an active part of the system toincrease the total pressure therein under abnormal operating conditions.

In refrigerating systems of the above type it is common practice toprovide a vent connection between active and normally inactive gascircuits, which vent may or may not include a separate vessel forholding a reserve quantity of inert gas out of circulation. Heretofore,this vent has been constructed in a manner that the inactive gas circuitis open at all times for flow of inert gas between the active andnormally inactive gas circuits with the result that, under certainconditions of operation, inert gas may be short circuited from theactive gas circuit through the vent and back to the active circuit.

This short circuiting may, for example, occur in absorptionrefrigerating systems of the air cooled type wherein the condenser isformed with two condensate drains leading from different sectionsthereof to different portions of the evaporator. When such a systemoperates under normal room temperature, say up to 80 F., all of therefrigerant vapor supplied by the generator is condensed in the firstsection of the condenser and the resulting liquid refrigerant fiows fromthis section of the condenser to the evaporator. Under these conditionsthe second section of the condenser, the vent line between thiscondenser section and the active gas circuit and the second drainbetween the condenser and the evaporator will be filled with inert gasweak in refrigerant Vapor.

Now then, with an increase in room temperature, say to 100 F., all ofthe refrigerant vapor furnished by the generator cannot be condensed inthe first section of the condenser, therefore, ammonia vapor will passinto the second section of the condenser displacing the mixture of inertgas and refrigerant vapor therefrom and through the vent into the activegas circuit thereby raising the total pressure in the system with theresult that refrigerant vapor begins to condense in the second sectionof the condenser. However, since the vent conduit, filled with a mixtureof inert gas and refrigerant vapor, is in open communication with thesecond section of the condenser, and since the vapor pressure ofrefrigerant in this mixture is relatively low, the liquid refrigerantdraining from the second section of the condenser will not reach theevaporator but will evaporate and diffuse into the inert gas in thesecond drain thereby setting up a short circuit through the second drainand the vent conduit to the active gas circuit.

An object of our invention is to prevent short circuiting of inert gasbetween the active and normally inactive inert gas circuits of arefrigerating system of the above type.

The above and other objects and advantages of our invention will be morefully understood from the following description taken in conjunctionwith the accompanying drawing in which:

Fig. l is a more or less schematic illustration of a refrigeratingapparatus embodying our invention; and

Fig. 2 is a detail section of a part of the apparatus illustrated inFig. 1.

Referring now to Fig. 1 of the drawing, our improved refrigeratingsystem includes generally, a generator assembly 10, an air cooledcondenser 11, a gas storage vessel 12, an evaporator 13, a gas heatexchanger 14, an air cooled absorber 15, a liquid heat exchanger 16, ananalyzer 17 and conduits interconnecting said elements to providecircuits for flow of a refrigerating medium, an absorption solution andan inert pressure-equalizing gas. The system is charged, for example,with a refrigerant-absorbent solution wherein ammonia is the refrigerantand water the absorbent, and wherein hydrogen is the inertpressure-equalizing gas.

The generator 10 includes a pump chamber 18, a weak solution chamber 19and a flue 20, which flue passes through the pump chamber and the weaksolution chamber. Suitable means, such as a gas burner 21, is providedfor heating the generator. A separating vessel 22 is connected to theupper part of the weak solution chamber 19. A vapor-lift pump 23 leadsfrom the upper part of the pump chamber 18 and is connected to the upperend of the separating vessel 22 above the uppermost part of the weaksolution chamber 19. The separating vessel 22 is connected by a conduit24 to the lower portion of the analyzer 17, and the upper portion of theanalyzer is connected by a conduit 25 to the inlet end of the condenser11. An air cooled rectifier 26 is provided in the conduit 25.

The condenser 11 is formed of a lower section 11*- and an upper section11 The evaporator 13 is formed of a lower section 13 and an uppersection 13 The lower section 11 of the condenser is connected by aconduit 27 to the lower section 13 of the evaporator. This conduit,which forms a liquid trap between the condenser and the evaporator, isprovided with a refrigerant precooler in the form of a coil 28 that iswrapped around and placed in thermal contact with the upper portion ofthe gas heat exchanger 14. A conduit 29 connects the outlet of section11 of the condenser to the inlet of section 11*, and a conduit 30, inthe form of a liquid trap, connects the outlet of section 11 of thecondenser to the upper section 13* of the evaporator.

The weak solution chamber 19 of the generator is connected by a conduit31, an inner pasage 32 of the liquid heat exchanger 16, and a conduit 33to an uppermost section 15 of the absorber. A conduit 34 connects theoutlet end of section 15 of the absorber to the next lower section 15'thereof. The lower portion of the absorber is connected by an absorbervessel 35, a conduit 36, an outer passage 37 of the liquid heatexchanger, a conduit 38, the analyzer 17, and a conduit 39 to the pumpchamber 18 of the generator.

The upper part of the absorber is connected by a conduit 40, an outerpassage 41 of the gas heat exchanger and a conduit 42 to the inert gasinlet end of section 13 of the evaporator. The inert gas outlet end ofthe evaporator section 13 is connected by a conduit 43 to the inert gasinlet end of the evaporator section 13 and the outlet end of thisevaporator section is connected by a conduit 44, an inner passage 45 ofthe gas heat exchanger, a conduit 46, and the absorber vessel to thelower end of the absorber. A drain conduit 47 connects the lower part ofthe evaporator section '13 with the inner passage of the gas heatexchanger. Also, so that condensate may drain from the outer gas heatexchanger 14.

passage of the gas heat exchanger into conduit 46, the

' upper end of conduit 46 extends into and is slightly smaller 5 thanthe lower end of the conduit which forms the inner passage 45 of the gasheat exchanger.

Corning .now to the present invention we connect the upper part of thegas storage vessel 12 to the conduit 30 leading from the outlet of thecondenser section 11 by a vent conduit 48. A second conduit 49 connectsthe lower part of the storage vessel 12 to a horizontal portion of theconduit46 between the gas heat exchanger 14 and the absorber vessel 35.As shown in Fig. 2, the

vent conduit 49 includes an enlargedportion 50, and the lower part ofthis conduit is submerged in a sump or trap 52 arranged in thehorizontal portion of the conduit 46.

Our invention has been illustrated anddescribed in connection with arefrigerating apparatus wherein a separate'storage vessel (vessel 12) isused to hold hydrogen in reserve under normal operating conditions.However, the storage vessel, as such, may be omitted, in which case thesection 11 of the condenser and the vent conduits 48 and 49 would beconstructed'and arranged so as to hold hydrogen in reserve under normaloperating conditions.

The operation of the system in general is as follows:

Heat is. applied to the generator 10 by the gas burner 21. The generatorcontains a solution of refrigerant medium in absorption liquid, forexample, ammonia dissolved in water. With heat applied to the generator,refrigerant vapor .is expelled from solution the pump chamber 18, whichvapor lifts absorption solution through a the vapor-lift 23 intotheupper portion of the separating vessel 22, from whence the absorptionsolution flows into the weak solution chamber 19 wherein additionalheatis applied to the solution in this chamber and additional refrigerantvapor is expelled therefrom. The refrigerant vapor from the vapor-lift23 and from the weak solution chamber 19fiows from the upper portion ofthe vessel 22'through the conduit 24 into and through the analyzer 17 incounterflow relation with strong refrigerantabsorbent solution, whichlatter solution flows through the conduit 38. into the the opposite endof the analyzer. From the analyzer the refrigerant vapor flows throughthe conduit 25 and the rectifier 26 into the inletof section 11 of thecondenser.

Assuming that the system is operating under normal temperatureconditions and that the first condenser section .11? has sutlicientcondensing surface so that all of the refrigerant vapors from thegenerator are condensed in this section of the condenser. Under theseconditions conduit 29, the condenser section 11*, conduit 30, conduit48, the gas storage vessel 12 and vent conduitr49 will be filled with amixture of hydrogen weak in ammonia vapor, and the fiuid in theseelements will stand more or less dormant; The refrigerant vapor in thecon- 5 denser section 11 condenses to liquid, giving up its heat ofcondensation to air flowing over this condenser section, and the liquidrefrigerant flows through conduit 27 and the precooler 28 into the upperpart of section 13 of the evaporator. In passing through the precooler,the liquidrefrigerant is cooled by transfer of heat therefrom to coldrich gas passing through the upper portion of the Inert gas weak inrefrigerant flows through conduit 42 into the gas inlet end of section13 of the evaporator, Wherefore the-liquid refrigerant evaporates anddilfuses into the inert gas producing the desired refrigerating effect.The partially enriched inert gas flows from section 13 ofthe evaporatorthrough conduit 43 into section 13 of the evaporator and from there,assuming that no liquid refrigerant is being conveyed to this section ofthe evaporator, the partially enriched inert gas flows through conduit44, the inner passage 45 of the gas heat exchanger, conduit 46, and theabsorber vessel 35 into the lower portionof the absorber.

Absorption solution weak in refrigerant is conveyed 7 of inert gas andrefrigerant vapor, wherefore the refrigerant vapor is absorbed in theabsorption solution. The

inert gas stripped of refrigerant vapor flows from the upper part of theabsorber through conduit 40, the outer passage 41 of the gas heatexchanger and conduit 42 back to section 13*? of the evaporator.

The absorption solution enriched in refrigerant vapor flows from thelower portion of the absorber into the absorber vessel 35, and fromthere theenriched absorption solution flows through conduit 36, theouter passage 37 of the liquid heat exchanger, and conduit'38 into theupper portion of the analyzer 17. In the analyzer, the enrichedabsorption solution flows in countercurrent relation with refrigerantvapor en route from the generator.

From the analyzer, the rich absorpto the condenser. tion solution flowsthrough conduit 39 into the pump chamber 18, wherein refrigerant vaporis expelled from solution and the absorption solution is lifted throughthe vapor-lift pump 23 into the separating vessel 22 of the generator,as explained above. Weak absorption solution flows from the lowerportion of the weak solution chamber 19 through conduit 31, the innerpassage 32 of the liquid heat exchanger, and conduit 33 back to theupper portion 15* of the absorber.

Referring now with more particularity to the present invention, thevessel 12, usually referred to as a pressure vessel, provides for areserve quantity of hydrogen, which upon increase in ambient temperatureis displaced by uncondensed ammonia vapor which flows from the condensersection 11 through conduit 48 into the vessel 12, forcing the hydrogenthrough vent conduit 49 and into the 'active gas circuit. Displacementof the hydrogen from storage in the vessel 12. into the active gascircuit is accompanied by a rise in total, pressure in the system 7 sothat all of the ammonia vapor supplied to the condenser is condensedtherein and refrigeration continues under the high ambient temperatureconditions.

The control function of submerging the lower end ofv vent conduit 49 inthe sump 52 may probably be best understood by first considering whatwould happen if the vent conduit 49 were not submerged in the sump 52.Assuming high ambient temperature conditions, all of the ammonia vaporsupplied by the generator will not be condensed in the section 11 of thecondenser. Under these conditions, ammonia vapor will pass throughconduit 29 into section 11* of the condenser. Since the trap in conduit30 between section 11 of the condenser andsection 13 of the evaporatoris filled witha mixture of inert gas weak in refrigerant rather thanwith liquid refrigerant, a short circuit will be established betweensection 13 of the evaporator and the absorber by way of conduit 30,conduit 48, storage vessel 12, vent conduit 49, conduit 46 and theabsorber vessel 35. Now then, as the total pressure in the system is,'raised by the displacement of hydrogen from the storage vessel 12 intothe active gas circuit, ammonia vapor will condense into liquid ammoniain section 11 of the condenser and drain therefrom into conduit, 30.However, since conduit 39 is filled with inert gas weak in refrigerant,the partial pressure of ammonia vapor' in this conduit will berelatively low and the liquid re- 7 frigerant that flows into thisconduit will evaporate therein and the mixture of inert gas andrefrigerant vapor produced thereby will flow therefrom to the absorberby way of the short circuit path just described.

With our invention, however, by submerging the lower 7 portion of thevent conduit 49 in liquid in the sump 52, short circuiting of gasbetween the evaporator and the absorber is prevented and refrigerantvapor condensed in the section 11 of the condenser will soon fill thetrap in conduit 30 and flow therethrough into section 13 of theevaporator wherein the liquid refrigerant evaporates and diffuses intothe partially enriched gas flowing therethrough from section 13 of theevaporator. It is necessary, however, for vent conduit 49 to alsofunction in reverse. In other Words, with a return to normal operatingconditions the pressure in the condenser will fall below that of theevaporator and absorber, and an equalizing effect will take placethrough vent conduit 49. Therefore, it is imperative that this ventconduit be submerged a fixed and constant amount. This is accomplishedby placing the sump 52 in the horizontal portion of conduit 46 and usingcondensate from the gas heat exchanger which drains back to the absorbervessel 35 through the pipe 46 to keep the sump filled to a predeterminedlevel. When the above mentioned pressure equalization occurs, liquid inthe sump 52 will be drawn up into vent pipe 49 until this liquid reachesthe enlarged portion 50 of the vent pipe where the slug of liquid willbreak and allow the gas to pass up through the vent pipe 49 into thepressure vessel 12. The liquid will then fall back into the sump 52.

While we have illustrated and described but one embodiment of ourinvention, it obviously may take other forms and be variously appliedwithin the scope of the following claims.

What is claimed is:

1. A refrigerating system including a generator, a condenser, anevaporator, an absorber, means for supplying vaporous refrigerant tosaid condenser, means for conveying liquid refrigerant from saidcondenser to said evaporator, means for supplying absorption liquid tosaid absorber, means forming a circuit for circulating an inert gasbetween and through said evaporator and absorber, a vent conduit betweensaid condenser and said inert gas circuit, and a connecting conduitbetween said vent conduit and said evaporator, said vent conduit havingmeans therein arranged to accumulate liquid refrigerant from saidevaporator to block and unblock flow of inert gas through said ventconduit responsive to a change in operating conditions within thesystem.

2. A refrigerating system including a generator, a condenser including afirst and a second section, an evaporator including a first and a secondsection, an absorber and conduits interconnecting said elements andforming therewith a first circuit for flow of a refrigerating medium, asecond circuit for flow of an inert pressure equalizing gas and a thirdcircuit for flow of an absorption solution, said conduits including afirst conduit connecting the first section of the condenser to the firstsection of the evaporator for flow of liquid refrigerant therethronghand a second conduit connecting the second section of the condenser tothe second section of the evaporator for flow of liquid refrigeranttherethrough, a vent conduit connected for flow of inert gas between therefrigerating medium circuit and the inert gas circuit, and meanscommunicating with the vent conduit and the inert gas circuit forblocking and unblocking flow of inert gas through said second conduitresponsive to a change in operating conditions within the system, saidmeans including a liquid trap connected to one of said evaporatorsections for receiving liquid therefrom to fill the trap.

3. A refrigerating system as set forth in claim 2 in which said liquidtrap is formed in said inert gas circuit.

4. A refrigerating system as set forth in claim 2 in which said liquidtrap is formed in said inert gas circuit and in which one end of saidvent conduit is submerged in liquid in said trap.

5. That improvement in the art of refrigeration by the aid of anabsorption refrigerating system which comprises circulating arefrigerant through a main circuit, circulating a pressure equalizinggas through an auxiliary circuit which coincides in part with said maincircuit, liquefying refrigerant at a point in said main circuit undernormal conditions, passing a portion of said refrigerant beyond saidpoint in the main circuit without being liquefied under abnormalconditions, storing excess pressure equalizing gas in said system in athird circuit which coincides in part with said auxiliary circuit,displacing the stored pressure equalizing gas into said auxiliarycircuit under abnormal conditions by uncondensed refrigerant from saidmain circuit, blocking circulation of pressure equalizing gas in saidthird circuit by an accumulation of excess liquid refrigerant flowingfrom a point of vaporization in said main circuit, and unblockingcirculation of inert gas in said third circuit responsive to anoperating condition within the system.

References Cited in the file of this patent UNITED STATES PATENTS2,069,865 Ullstrand Feb. 9, 1937 2,136,600 Ullstrand Nov. 15, 19382,252,791 Ullstrand Aug. 19, 1941 2,306,199 Ullstrand Dec. 22, 19422,402,416 Kogel June 18, 1946 2,484,669 Backstrom Oct. 11, 1949

